We're increasingly using our smartphones to do more and more - and now they can help us navigate, plot courses, play podcasts and of course take damn good photos and videos whilst out on our walks. But this all has a big price in battery life. And with most phones now having non-removeable batteries, now you can't swap them either.

The answer? A power bank. In essence another battery which you charge up in advance (very important that bit) and then use to charge / power your phone. So here's our selection of the Top 5 Power Banks available now.

As we get to see new kit, we'll be updating this page, so keep popping back to stay up-to-date with our selection.

Solar Technology Freeloader iSIS

Once upon a time, solar charging was a bit of a joke... taking literally days to charge devices - especially here in Britain. But now solar technology is starting to be a serious option for charging walkers' devices. And leading the pack is the Freeloader iSIS.

Obviously, charging times depends on the sunlight available, but the solar cell on the iSIS is upto 50% more efficient than others, and can fully charge the average smart phone 3 times at full capacity. Thanks to its' built-in charging arms, it will happily charge either Lightning or Micro USB devices, and a built-in stand allows you to angle the iSIS at the sun at all times - or you can even attach it to your backpack.

And if you have no sunlight at all, the iSIS can be charged back at base in the usual fashion by plugging it into a Mains USB charger - and will still provide charging for devices whilst out on the hill.

If you need flexibility whilst on the hill, then the Powermonkey Sport 25 is difficult to beat. The unit houses a lightweight yet powerful 6700mAh lithium-ion battery, capable of recharging a GoPro Hero5 four times and a Garmin Edge 1000 four times. It is also compatible with a plethora of other 5V devices such as smartphones, tablets (including iPad), iPods, digital cameras, sat phones and more.

But what's makes it different is the Sport 25 is waterproof for 30 minutes in up to 1 metre of water - and that's why it has an Ingress Protection (IP) rating of 67.

Also - and this could be a life-saver - the Sport 25 features a powerful integrated 150 Lumen torch which also has an SOS mode should you get caught in an emergency situation and at just 187g it's perfect to slip into your pack to keep your devices charged.

So eagre were power experts Aukey to sell the virtues of their new 26,500mAh power bank they sent it to us for review before it was even available in the UK. It's now available here, as is the smaller capacity version too.

This is a monster of a device - whereas some other power banks are 2,000mAh - meaning they'll charge the average smartphone once - this an outstanding 26,500mAh! That's enough to charge the average phone around ten times on one charge. And because it's equipped with Quick Charge 3.0 technology, it can charge devices up to 4 times faster than normal chargers - providing you have a compatible device. But even if you haven't, it can charge all 5V USB powered devices including Android and Apple phones faster too.

In addition, it will also happily charge up tablets, unlike other power banks, and you'll be able to charge 9.7-inch iPad Pro twice on one charge, with a bit left over for a phone too. Also, it has a Lightning connector as well as a micro USB, so if you are an Apple geek, you don't need a micro USB cable to charge the power bank up.

If you're outdoors a lot and have several pieces of USB-chargable kit, then this is a must...